Indoor cellular systems are becoming increasingly spread as user demands for everywhere coverage are matched by the opportunity for mobile operators to offer improved services and increase traffic revenues. The owners of the building in which the indoor cellular system is provided also benefit from such a system as the value of their property and their ability to attract and retain key tenants increases.
It is estimated that two thirds of all calls are made from inside a building and with the increased demands for high data traffic capabilities there is a growing need for improved capacity and coverage from indoor users.
An in-building cellular system offloads surrounding macro sites and ensures a higher quality of service for indoor users.
One of the basic components provided in a distributed antenna system (DAS) is the power splitter, which divides the power from a radio base station for distribution to several antennas. The splitter distributes the signal equally to multiple antennas and is normally a passive component that has one input and several outputs. The splitter is a RF component which cannot amplify the input signal and splits it at the output only. By way of example in case of a 2-way splitter, the splitter splits the input signal into two equal output powers, whereas, in case of a 3- or 4-way splitter, the splitter splits the input signal in three and four equal output power signals, respectively. The 4-way splitter, by way of example, splits power fed at its input equally to each of the four antennas connected to the respective output port.
This traditional splitter does not consider the traffic load at the antennas connected to its ports so that the power will be split independently of the number of mobile stations (MS) connected to the antennas. With the current architecture of a power splitter it is not possible to optimize the power and to manage the power distribution flexibly in terms of carried traffic by each antenna. Thus a big part of the radio base basis station power is wasted in the indoor distributed antenna system.